Dry etching is the most important technology used for patterning interlayer insulating film material, wiring material etc. in the production of semiconductor circuit elements.
Dry etching is a technology wherein a pattern is formed by coating a photoresist onto a substrate on which a film of interlayer insulating film material, wiring material, etc., has been formed by means of sputtering, CVD, electrolytic plating, spin coating, etc., and by exposing and developing the photoresist and wherein the pattern of interlayer insulating film and wiring pattern are then formed by dry etching with a reactive gas using said photoresist as a mask. Ordinarily, the substrate is treated by ashing after dry etching, and after removing the photoresist which had been used as a mask by ashing, residues partly remaining such as photoresist residues etc. are further removed with a photoresist stripping liquid.
However, the photoresist residues which remain after dry etching cannot be completely removed with the photoresist stripping liquids generally used in the prior art which combine an organic solvent with alkanolamine (e.g., JP, A, 5-281753; U.S. Pat. No. 5,480,585). The reason for this is thought to be that, together with the etched material, part of the photoresist residues remaining after ashing becomes inorganic. Therefore, removing liquids containing fluorine compounds (JP, A, 7-201794; EP, A, 662705), hydroxylamine (U.S. Pat. No. 5,334,332) and quarternary ammonium compounds (JP, A, 8-262746; U.S. Pat. No. 5,567,574) have been proposed for removing photoresist residues after dry etching.
However, these removing liquids for photoresist residues, if any thereof remains, corrode the wiring material; therefore, it is necessary to rinse with an organic solvent such as isopropyl alcohol etc. and to perform the treatment at a high temperature to remove the photoresist residues completely. Moreover, because the liquids include organic compounds at a ratio of some 10% to 100%, these removing liquids for photoresist residues are a heavy burden on the environment and therefore not desirable.
Further, the wiring material is also corroded when the photoresist residues are removed, because the wiring material and the photoresist residues are similar composition. Consequently, photoresist stripper compositions comprising sorbitol etc. have been proposed (JP, A, 8-262746; U.S. Pat. No. 5,567,574).
Furthermore, the inventors of the present invention have disclosed a removing liquid for photoresist residues containing aliphatic carboxylic acids and their salts (JP, A, 11-316464). This removing liquid does not contain organic solvents, which means that the burden on the environment is small, and it can be used without corroding metallic wiring of Al—Si—Cu, Al—Cu, W, Ti, TiN, etc., However, together with the miniaturization of the wiring that has been taking place in recent years, etching and ashing conditions have become more severe and resist residues have come to be more firmly attached. Therefore, treatments at high temperatures and for long durations are necessary to completely remove resist residues, as a result of which Al—Si—Cu and Al—Cu have at times been corroded. Thus, compared to the stripping liquids of the prior art, agents inhibiting corrosion with a high corrosion inhibiting effect are required.
Further, multilayer wiring structures have generally been introduced to semiconductor circuit elements wherein the upper aluminum wiring and the lower aluminum wiring are connected by forming via-holes in the interlayer insulating film and by embedding a metal such as tungsten etc. in these via-holes. With semiconductor circuit elements of relatively large dimensions, there is a complete match between the upper wiring and the via-holes, and the via-holes are covered by the upper wiring. However, together with the miniaturization of semiconductor circuit elements that has been taking place in recent years, a high degree of accuracy is being required for forming wiring and via-holes; therefore, dislocations between the wiring and the position of the via-holes, not matching completely, occur and with the via-holes not completely covered, tungsten or other embedded metals may be exposed by the side of the upper wiring.
This type of wiring structure is called borderless via structure; and when forming wiring on top of via-holes of a borderless via structure, resist residues are attached to the surface of the upper wiring and the tungsten embedded in the via-holes. When using the above-mentioned strongly alkaline removing liquids for resist residues containing hydroxylamine or quarternary ammonium compounds for removing these resist residues, there is the problem that the tungsten is dissolved due to an electrochemical reaction. Therefore, a removing liquid containing ammonium phosphate has been proposed (JP, A, 2000-232063). However, when the resist residue removing properties are insufficient, it is necessary to add a surfactant, in which case there is the environmental burden to be considered because of the phosphate compounds.
On the other hand, new wiring materials and interlayer insulating film materials have come to be used together with the increase in performance and the miniaturization of semiconductor circuit elements that has been taking place in recent years, the result of which has been that limits have appeared in the way the removing liquids for photoresist residues of the prior art have hitherto been used.
For example, with the demand for an increased performance and the miniaturization of semiconductor circuit elements, the introduction of Cu wiring has been considered with the aim of reducing the wiring resistance and it has become possible to form Cu wiring by means of the damascene process. The damascene process is a process for forming a wiring pattern wherein the wiring pattern is formed as trenches in the interlayer insulating film and wherein, after the Cu has been embedded by sputtering or electrolytic plating, the excess blanket Cu is removed by chemical mechanical polishing (CMP) etc.
As resist stripping liquid for this new wiring material, i.e., Cu wiring material, there are stripping liquids containing triazole compounds as Cu corrosion inhibitor (JP, A, 2001-22095; JP, A, 2001-22096; JP, A, 2000-162788); however, these stripping liquids, in the same way as described above, have to be used at high temperatures, need to be rinsed with isopropyl alcohol etc. and also present the problem of containing organic solvents. Further, there is also a resist stripping liquid composition comprising benzotriazole derivatives as Cu corrosion inhibiting agents (JP, A, 2001-83712); however, this composition also comprises an aqueous organic solvent and involves the above-mentioned problems. Furthermore, having poor biodegradation properties, triazole compounds and benzotriazole derivatives involve a considerable liquid waste disposal problem. Moreover, since triazole compounds and benzotriazole derivatives do not easily dissolve in water, these corrosion inhibiting agents remain on the wafer surface after rinsing with water, which can have a negative effect on subsequent work processes.
On the other hand, with the demand for an increased performance and the miniaturization of semiconductor circuit elements, the introduction of interlayer insulating films with a low dielectric constant (so-called low-k films) has also been considered in recent years. Low-k films generally are organic films represented by aromatic aryl compounds, siloxane films represented by hydrogen silsesquioxane (HSQ) and methyl silsesquioxane (MSQ) and porous silica films. When forming the trenches of the upper wiring and the via-holes connecting the lower Cu wiring with the upper wiring in the production of semiconductor circuit elements using these types of wiring material and interlayer insulating film material, the interlayer insulating film material or different low-k films are dry etched and photoresist residues are formed which have a different composition from those formed when using conventional wiring materials and interlayer insulating film materials. Further, compared to conventional wiring materials and interlayer insulating film materials, Cu and different types of low-k films have a poor chemical resistance; hence, it is not possible to use conventional photoresist residue removing liquids for aluminum wiring as they are to remove the photoresist residues remaining after dry etching. For example, the alkanolamine, quarternary ammonium compounds and fluorine compounds contained in the above-mentioned removing liquids for photoresist residues cause the corrosion of Cu which has a low corrosion resistance and the alkanolamine and quarternary ammonium compounds cause the deterioration of the film, the change of the structure, the change of the dielectric constant and a change in the mechanical strength etc. of the different low-k films. It is further desirable to remove the photoresist at low temperatures because the low-k films have a poor chemical resistance.
Thus, various corrosion inhibiting agents for these new materials have been considered, without, however, obtaining any satisfactory results up to now, as there are no acidic removing liquids with sufficient corrosion inhibiting effect which do not have a negative effect on the environment.
A problem to be solved by the present invention is to provide, in the production of semiconductor circuit elements, a photoresist residue removing liquid for removing photoresist residues which are generated when ashing and dry etching substrates provided with conventional metallic wiring using Al—Si—Cu, W, Ti, TiN, etc. under conditions more severe than in the prior art and which are attached more firmly than in the prior art without corroding the wiring.
A further problem to be solved by the present invention is to provide, in the production of semiconductor circuit elements, a photoresist residue removing liquid for removing photoresist residues which have a different composition from conventional photoresist residues and which are generated when ashing and dry etching substrates provided with metallic wiring using the new wiring material Cu without corroding the wiring.
A further problem to be solved by the present invention is to provide, in the production of semiconductor circuit elements, a photoresist residue removing liquid for removing photoresist residues which have a different composition from conventional photoresist residues and which are generated when ashing and dry etching a substrate provided with an interlayer insulating film with a low dielectric constant without leading to the deterioration of the film, the change of the structure, the change of the dielectric constant or a deterioration of the mechanical strength etc. of the interlayer insulating film.
A further problem to be solved by the present invention is to provide, in the production of semiconductor circuit elements, a photoresist residue removing liquid for removing photoresist residues which are generated when ashing and dry etching substrates provided with conventional metallic wiring using Al—Si—Cu, W, Ti, TiN, etc. under similar conditions as in the prior art without corroding the wiring.
A further problem to be solved by the present invention is to provide, in the production of semiconductor circuit elements, a photoresist residue removing liquid for removing photoresist residues which are generated when ashing and dry etching substrates provided with metallic wiring which is connected by via-holes and wherein the metal embedded in the via-holes is partly exposed without dissolving the exposed metal embedded in the via-holes.
A further problem to be solved by the present invention is to provide, in the production of semiconductor circuit elements, a photoresist residue removing liquid for effectively removing photoresist residues which are generated when ashing and dry etching even at low temperatures.